The present invention pertains to the field of integrated circuit device manufacturing processes. More particularly, this invention relates to a method of forming narrow spacers or spaces in semiconductor devices for use in forming components of reduced size.
The size of components on semiconductor wafers is typically limited by the resolution of the optical lithography printing system. In an optical lithography printing system, radiation is directed from an illuminating source through a patterned mask and onto a photoresist layer. The patterned mask transmits the illumination source radiation onto selected areas of the photoresist layer to reproduce the mask pattern in the photoresist layer. Resolution in optical lithography systems is limited by diffraction effects, which spread radiation from the illumination source into regions of the photoresist which are not directly exposed to the illumination source. Because of these diffraction effects, there is a minimum distance beyond which even a geometrically perfect lens cannot resolve two points. In other words, when two points are less than a minimum distance from each other, the two points cannot be resolved by the lithography system. The diffraction patterns associated with each point overlap each other to such an extent that the two points cannot be effectively differentiated. The resolution of the lens depends on the wavelength of the illumination source and the numerical aperture of the lens.
As process technologies approach and surpass the resolvable limits of current lithography systems, it is has become increasingly difficult to create the narrow spaces that are now required in semiconductor fabrication processes. Many of the current photolithography systems in use have difficulty creating spaces smaller than 0.2 microns. However, by minimizing the area required for a given component, the number of components available for a given area of silicon increases, and with it a corresponding increase in the circuit complexity that can be achieved on a given area of silicon. Thus, decreasing the size of various components of semiconductor devices allows for more components to be formed on a single silicon wafer, leading to substantial savings in the fabrication costs of semiconductor devices.
Therefore, it would be desirable to have a manufacturing process that permits the reproducible fabrication of semiconductor device components having critical dimensions that are smaller than the minimum resolvable feature of current photolithography systems.
The present invention solves the problem of overcoming the resolution limits of conventional photolithography when patterning small or narrow spaces in semiconductor devices. To allow for very small separations between conducting portions, small insulating spacers are formed which separate conducting portions.
In one aspect of the invention, a method for reducing the minimum size of a component is provided. The method includes forming one or more insulating spacers on a surface of a semiconductor wafer, the spacers having a lateral width less than the minimum width resolvable by a photolithography system.
In another aspect of the invention, a method is provided for forming at least one insulating spacer on a semiconductor structure. The method includes providing a semiconductor structure having a substrate, an insulating layer on the substrate, the insulating layer having one or more exposed portions and one or more unexposed portions, and a photoresist layer covering the one or more unexposed portions of the insulating layer. The exposed portion of the insulating layer is isotropically etched in order to form one or more insulating spacers, each spacer having a lateral width less than a minimum width resolvable by a photolithography system.
In yet another aspect of the invention, a method is provided for forming at least one insulating spacer on a semiconductor structure. The method includes providing a semiconductor structure having a substrate, an insulating layer on the substrate, the insulating layer having one or more exposed portions and one or more unexposed portions, and a photoresist layer covering said one or more unexposed portions of the insulating layer. The lateral width of the photoresist layer is then trimmed, thereby widening the exposed portion of the insulating layer. The exposed portion of the insulating layer is then etched in order to form one or more insulating spacers, each spacer having a lateral width less than a minimum width resolvable by a photolithography system.
In another aspect of the invention, a method is provided for forming small components on a semiconductor wafer. The method includes forming one or more insulating spacers on a surface of a semiconductor structure, where the insulating spacers having a lateral width less than a minimum width resolvable by a photolithography system. A conducting layer is then deposited over the one or more spacers. Finally, a component is formed from the conducting layer.
In yet another aspect of the present invention, a method is provided for removing a narrow spacer from a semiconductor structure. The method includes providing a semiconductor structure having one or more insulating spacers adjacent one or more conductors, wherein the one or more spacers are formed from a spacer material that will evaporate at an evaporative temperature below a temperature that will damage the one or more conductors. The semiconductor structure is then heated to evaporate the one or more spacers and thereby remove them from the semiconductor structure.